RE: Best CI for process

Joe,

I am using the term literally. Dmax is the absolute highest density,
Dmin is the absolute lowest density. The difference between the two
is not the actual printing DR of the negative since you have to
consider both the toe and shoulder to determine useful density range
for your process. And this is one of the reasons I don't find the
term density range, if expressed without taking into account the toe
and shoulder, to be useful, at last not for sharing information with
others. The other reason I don't find it useful is because most films
have what we might called gama finity, that is, beyond a certain
point you can increase the density range but the slope of the curve,
which determines the effective printing contrast, does not increase.

Sandy

>Sandy,
>
>In the context of your practice can you define dmin, dmax, and density
>range for me? I've found different authors use these terms (especially
>density range) as if they are speaking to some commonly accepted
>standard, yet they often derive them differently.
>
>One of the nice things about Contrast Index is that it is defined quite
>precisely and is unequivocal.
>
>Thanks,
>
>Joe
>
>>>> sanking@clemson.edu 10/02/05 12:14 PM >>>
>Eric,
>
>Sorry, but a part of my last message was omitted during cut and paste.
>
>What I meant to have said was that although density range and CI (or
>Gamma, Average Gradient or whatever you want to call it) are related,
>the use of the former to talk about negative contrast can be very
>misleading because it often does not provide a good indicator of the
>effective printing density of a negative, while CI nearly always does.
>
>For example, consider the following three cases, which correspond to
>data from testing I did of TRI-X film, at nine minutes, 13 minutes
>and 20 minutes.
>
>Time Dmin Dmax DR CI
>9:00 .23 2.80 2.57 1.0
>13:00 .30 3.11 2.81 1.0
>20:00 .45 3.35 2.90 1.0
>
>As you can see, the DR increases significantly with time of
>development, but the CI, which is a much better indicator of
>effective printing density, does not. The negative developed for nine
>minutes will print with exactly the same contrast as the one
>developed for twenty minutes, though the extra B+F of the twenty
>minute negative will require more printing time. In other words,
>increasing time of development to obtain a higher DR range over that
>needed for maximum CI is just a waste of time which also results in
>longer printing times.
>
>
>Of course, if you are working with a film that has very linear
>straight line curve there will be a better correlation between DR and
>CI.
>
>Sandy
>
>
>
>
>
>
>>Sandy, I know they are.
>>
>>Eric Neilsen Photography
>>4101 Commerce Street
>>Suite 9
>>Dallas, TX 75226
>>http://e.neilsen.home.att.net
>>http://ericneilsenphotography.com
>>
>>> -----Original Message-----
>>> From: Sandy King [mailto:sanking@clemson.edu]
>>> Sent: Saturday, October 01, 2005 11:03 PM
>>> To: alt-photo-process-l@sask.usask.ca
>>> Subject: RE: Best CI for process
>>>
>>> Eric,
>>>
>>> Density range (DR) and contrast index (CI) are closely related.
>>>
>>> Read about it.
>>>
>>> Sandy
>>>
>>>
>>>
>>>
>>>
>>> >
>>> >
>>> > So a discussion of density range may be more appropriate than the
>CI
>>> for in
>>> >camera negatives intended for use in platinum/palladium printing?
>>> >
>>> >
>>> >
>>> >Eric Neilsen Photography
>>> >4101 Commerce Street
>>> >Suite 9
>>> >Dallas, TX 75226
>>> >http://e.neilsen.home.att.net
>>> >http://ericneilsenphotography.com
>>> >
>>> >> -----Original Message-----
>>> >> From: Ryuji Suzuki [mailto:rs@silvergrain.org]
>>> >> Sent: Saturday, October 01, 2005 7:19 PM
>>> >> To: alt-photo-process-l@sask.usask.ca
>>> >> Subject: Re: Best CI for process
>>> >>
>>> >> From: Richard Knoppow <dickburk@ix.netcom.com>
>>> >> Subject: Re: Best CI for process
>>> >> Date: Sat, 01 Oct 2005 16:36:06 -0700
>>> >>
>>> >> > Is it possible for you to post it on your web site
>>> >> > perhaps as a PDF, I think it would be of considrable value.
>>> >>
> >> >> PDF papers are ideal in my view but I am reluctant to do this to
>my
>>> >> photographic paper file. I'd rather mail a photocopy to someone
>in
>>> >> serious, legitimate need of the information.
>>> >>
>>> >> Although I might not condemn anyone putting scans online
>quietly, I
>>> >> probably don't want to know if my copy has anything to do with
>it.
Received on Sun Oct 2 12:45:10 2005